generating the evaluation license key is very simple (you should create an account with Atlassian)

the product is installed for user "jira":
sudo su - jira

logs are in /opt/atlassian/jira/logs/

To troubleshoot webhooks, you should enable DEBUG loggin as default in http://localhost:8080/secure/admin/ViewLogging.jspa
then you see the webhook body being traced in /opt/atlassian/jira/logs/catalina.out